If you had previously tried to download an app on your iDevice's
data connection and it was larger than 20 MB, a popup would tell
you it couldn't be downloaded until you were on a WiFi network.

This change is big for a couple reasons -- first (and most
straightforwardly), this means that a lot more apps are available
to you when you're not connected to WiFi.

Secondly, it helps set a tone for the future of wireless
connectivity, that it should be faster and more readily
available. We're not sure what kind of conversation (if any)
Apple had with wireless carriers surrounding this change, but
there's no way they're unaware of it.

One possible reason for the adjustment is that the graphics
packages required to fill an iPad 3's retina display are much larger than
those for an iPad 2, so the limit was increased to make sure
more of these apps are readily available.

Besides, with Apple's new iPads boasting 4G LTE connectivity, they can make short work
of a 50 MB download.